Eclipse Java Tutorial

Eclipse Integrated Development Environment is an incredible open source compilation of tools, projects and co-existing working groups. Eclipse is the most used open source Java Integrated Development Environment because of its advanced text editor with numerous tools and plug-ins. It makes it easy and fast to write Java programs and run them. More updates can be added to Eclipse given its plug-in structure. The Eclipse platform is developed using the Java programming language and can be utilized to develop client applications, integrated development environments, and some other tools.

The major features of Eclipse include:

Windows builder
Integration using Maven
Mylyn
XML editor
Git client
CVS client
PyDev

Selecting a workspace

After installing Eclipse, the next step is to select a workspace for your projects. This refers to folders on your hard drive that you can store your project’s files and Java classes.

Components of an Eclipse window

The components that can be seen on opening an Eclipse window include the following;

Views
Editors
Menu bar
Toolbar

Several Eclipse Windows can be opened simultaneously, each showing a different perspective.

The Eclipse Menus include;

File menu
Help menu
Navigate menu
Run menu
Edit menu
Search menu
Project menu
Window menu

However, with plug-ins, which can be updated, you can add more menus and menu items.

An Eclipse Perspective

An Eclipse perspective is used to refer to an initial group, an arrangement of views and an editor area. Java is Eclipse’s default perspective. A user has the option of selecting from an open perspective or to open a new perspective.

Fig 1. Image of the Java window

The Eclipse Java Perspective

a. Package Explorer view

This gives the user space to browse the structure of their projects and to access files in an editor through double-clicking the file. It can also be used to alter the project’s structure by either renaming or move files and files by dragging and dropping.

b. Outline view

This displays the structure of the selected source file.

c. Problems view

Displays errors and caution messages. You can open it by going to the window, show view then problems. This view also allows the user to initiate a Quick fix by right-clicking on the selected messages.

d. Javadoc view

Displays the documentation of the chosen element in the Java editor.

e. Java editor

Can be used to change the structure of the Java source code. A click on the left side of the editor gives you an option of configuring the properties.

Fig 2. An example of creating a project in Eclipse

Creating a Java Program using Eclipse

To create a project;

Select file
Click on New
Select Java project
Enter com.username.eclipse.ide. one (as the title of your project – choose a package name you like, this is just an example)
Click on the Finish button

To create a package

After creating the com.username.eclipse.ide.one package, click on the src folder, right-click it then choose New then select Package. Press Finish button

Editing files

When you want to develop a new file that is a copy of one which is not within your present project, you can import it, using import command,

To edit an existing file

Go to navigator
If, for some reason, the files are not visible, click on the arrow near the project name.
Double-click on the file of your choice

How to import files (import command)

Go to files, then select import
Check that the triangle near the General is facing downwards
Select file system, then Next
Select Browse to look for your file
Enter your project title in the folder
Click finish

Creating Java class

This explains creating a new file which opens in the Java editor.

To create a Java class;

Right-click on the package
Click on New
Select Class to create a Java class
Enter MyFirstClassName as the class title
Click the public static void main (string[]args) checkbox
Press Finish button

Executing your project in Eclipse

To run your code either right-click on your Java class in the Package Explorer or right-click in the Java class and choose Run-as then select Java application. This command makes Eclipse run your Java Program, and the output is displayed in the console view.

How to set the Java Build Path

When compiling a Java project, we can make use of a Java build path so that we can discover dependent cases. It comprises the following items;

Code in the source folders
Jars and classes folder associated with the project
Classes and libraries exported by projects referenced by this project

The Java build path page enables us to see and alter its contents. It can be accessed by right-clicking on the Java project in the package explorer view then clicking the properties menu item. On the left-hand side, select Java build path.

Eclipse Web Tool Platform

This provides useful tools for creating Java web applications that execute in a Java environment. They include HTML, CSS and XML files. With Eclipse Web Tool Platform, the process is made user-friendly as these web artifacts have already been created.

How to build a Java project in Eclipse

A Java project is associated with a Java builder. To view the builders associated with a project;

Right-click on the particular project in the Package Explorer view
Select Builders in the left-hand side tree

A java builder separates a java project from others. It must compile the Java source code and generate new classes.

Debugging a Java program

For a fast method of debugging a Java program you should use the Package Explorer view, following these steps;

Right-click on the Java class that contains the method you want to debug
Click on Debug As
Select Java application

Special Issues dealing with Java Eclipse IDE

Before this check on the availability of Java Development tools (JDT) plugin, from the Window, then select Open perspective before checking to see if Java is listed. If not, you should download JDT.
Check for use project folder As Root for Sources and Classes before creating a project
During debug runs, Eclipse will stop before main(), all you need to do is click the select button.

Running a Java program outside of Eclipse

In this case, you have to export it as a JAR file, which the standard distribution format for Java applications.

Creating a JAR file

Choose your project then right-click for a drop-down options menu
Select the Export menu entry
Select JAR file then hit the next button
Choose your project from the list, enter your export destination and a title for the JAR file
Hit the Finish button

How to run your Program Outside Eclipse

Open a command shell or terminal.
Get back to the JAR file, by entering cd path_to_file
To execute this program, include the JAR file in your classpath, which refers to the Java classes that you can access in the Java runtime
Type java –classpath myprogram. Jar com.username.eclipse.ide.one.MyFirstclassName, which is a command, in the directory used to export.

The Breadcrumb

Activation of the breadcrumb mode for the Java editor enables you to navigate the source code directly from the Java editor. It can be done by right-clicking in the editor then select the show in breadcrumb entry. This activation makes it possible to navigate the source code from the editor. You can also conceal it by right-clicking on the feature, breadcrumb, then select hide.

Closing and opening Projects

You may want to focus all your attention on one project; this can be done by closing all other projects. Plus, closing projects saves runtime memory used by Eclipse hence decreasing the build time. Eclipse ignores closed projects such that all later searches ignore files from the closed project and the problem view also shows errors from the opened projects only.

To close a project, right-click on it and choose the close project menu. However, to close multiple unrelated projects right-click on it then select close unrelated projects. You can reopen a closed project by double-clicking on it then selecting open project.

The filter functionality for the Package Explorer view provides the options of hiding the closed projects.

Content Assist and Quick Fix

Content assist is a feature in Eclipse that provides the user with the ability to obtain context-sensitive code completion in an IDE upon user request. You can invoke this by pressing control and space buttons simultaneously.

Quick fix gives you some suggested replacements for an error that has been detected by Eclipse. The error will be underlined, select the particular text then simultaneously press, the buttons CTRL and 1. Quick fix allows you to come up with new local variables and fields not forgetting additional methods and new classes. Moreover, it can assign a statement to a variable and much other important material.

Conclusion

Most of Eclipse is written in the Java programming language making it more suitable as an IDE for developing greater platforms, application software and even IDEs through Java.